EP2526434A2 - Method for determining mechanical properties of magnetostrictive materials - Google Patents

Method for determining mechanical properties of magnetostrictive materials

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Publication number
EP2526434A2
EP2526434A2 EP11734388A EP11734388A EP2526434A2 EP 2526434 A2 EP2526434 A2 EP 2526434A2 EP 11734388 A EP11734388 A EP 11734388A EP 11734388 A EP11734388 A EP 11734388A EP 2526434 A2 EP2526434 A2 EP 2526434A2
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Prior art keywords
coefficients
magnetic field
fourier
determining
susceptibility
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EP11734388A
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German (de)
French (fr)
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EP2526434B1 (en
Inventor
Eckhard Quandt
Chrisoph Bechtold
Steffen Chemnitz
Claas Thede
Iulian Teliban
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Christian Albrechts Universitaet Kiel
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Christian Albrechts Universitaet Kiel
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
    • G01R33/16—Measuring susceptibility
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
    • G01R33/18—Measuring magnetostrictive properties

Definitions

  • the invention relates to a measurement and evaluation method with which mechanical stress states of magnetostrictive materials can be determined.
  • the invention is based on the magnetostrictive effect. Magnetostrictive sensors as well as various measuring and signal evaluation methods for these have been known for a long time. Roughly generalized, magnetostrictive sensors can be divided into two functional groups and two technological groups. One group exploits the magnetostrictive effect, the other the inverse magnetostrictive effect. In the technological classification, one of the magnetic or the magnetostrictive element is designed to be so flexible with respect to the other that with mechanical pressure at one of the element ends, the distance between them is changed. The change is exploited as a measuring effect.
  • Procedures and devices that exceed the evaluation result distance-independent of the distance sensor element / measurement object by a multiple of the measurement effect, are just as well known as evaluation circuits that provide a nearly linear measurement result to the voltage state of the magnetostrictive material.
  • the object of the invention is to provide an evaluation method which makes it possible to obtain a time-modulated signal which is characteristic of the magnetic properties of an inverse magnetostrictive material.
  • FIG. 1 shows an idealized magnetization curve
  • FIG. 2 shows a magnetic material in the sinusoidal alternating magnetic field.
  • FIG. 3 shows the coefficients of the Fourier series with multiples of twice the modulation frequency.
  • FIG. 4 shows the local minima as a function of the mechanical material.
  • FIG. 5a shows the Fourier coefficients as distance function between material and measuring coil
  • FIG. 5b the characteristic minima at distance increase
  • FIG. 6 shows the square-wave signal change with a varied Hmod.
  • FIG. 7 shows the zeros of the Fourier coefficients for different H mo ⁇ ratios.
  • FIG. 8 shows the proportional material anisotropy field for the modulation field with zeros and.
  • a ferromagnetic inverse magnetostrictive material becomes an alternating magnetic field of frequency f mo d. exposed.
  • the size of the alternating magnetic field is chosen so that the magnetic material is periodically brought to saturation.
  • the magnetization curve represented as the magnetization M of the material as a function of the external field strength H ext , this results in a characteristic course of the susceptibility over the
  • the saturation magnetization M s is reached at the field strength H k .
  • Susceptibility a square wave signal with the upper and lower values x and 0 respectively. It should also be noted that in addition to the amplitude of the square wave signal, the time interval in which the signal assumes the upper of the two values-corresponding to the duty cycle-varies with different voltage states.
  • the susceptibility as a function of time can be written as:
  • the coefficient a 0 is the constant component of x (t) and can be determined by
  • the time Ti can be increased by the limits of equation (3) in the ratio of Ht
  • Equation (-7) then comes together with
  • the amplitude of the coefficients thus decreases exponentially with the distance between the measuring coil and the magnetic material.
  • Figures 5a and 5b graphically depict the dependence of the coefficient of x.
  • the Fourier coefficients thus decrease exponentially with increasing distance x between the measuring coil and the material.
  • the characteristic local minima also occur with increasing distance at the same H * to H mo d.
  • the ratio H * to H mo d is therefore crucial for the formation of local minima.
  • the Fourier coefficients can also be calculated according to equation (7) for a changing H mo d at constant H *, as shown in FIG. 7.
  • the modulation field where zeros occur is therefore proportional to the anisotropy field of the material.
  • the modulation field can thus be a certain Fourier coefficient, z. B. Ü4, to zero.
  • the value of the modulation field in this zero position is correspondingly proportional to the anisotropy field of the material, which in turn is characterized by the stress state. If the stress state of the material changes and thus H k , the modulation field can be adjusted accordingly so that the Fourier coefficient remains zero. This possibility of variation of the modulation field Hmod. So provides another way of signal evaluation.

Abstract

The invention relates to a method for determining mechanical properties of magnetostrictive materials, comprising the following steps: introducing the material into an external alternating magnetic field, wherein the magnetic material is periodically saturated, applying an alternating mechanical tensile stress load in a direction perpendicular to the magnetic field direction, obtaining a characteristic curve of the susceptibility at various tensile loads, determining the coefficients of a Fourier series from the curves of the susceptibility, and determining the coefficients of the zero points of the Fourier function, which zero points present themselves as local minima.

Description

Verfahren zur Bestimmung mechanischer Eigenschaften magnetostriktiver Materialien Die Erfindung betrifft ein Mess- und Auswerteverfahren, mit dem mechanische Spannungs- zustände magnetostriktiver Materialien bestimmt werden können.  Method for Determining Mechanical Properties of Magnetostrictive Materials The invention relates to a measurement and evaluation method with which mechanical stress states of magnetostrictive materials can be determined.
Die Erfindung beruht auf dem magnetostriktiven Effekt. Magnetostriktive Sensoren sowie verschiedene Mess- und Signalauswerteverfahren für diese sind seit langem bekannt. Grob verallgemeinert einteilbar sind magnetostriktive Sensoren in zwei funktionale Gruppen und zwei technologische Gruppen. Die eine Gruppe nutzt den magnetostriktiven Effekt, die andere den inversen magnetostriktiven Effekt aus. In der technologischen Einteilung ist bei den einen das magnetische oder das magnetostriktive Element gegenüber dem anderen derart flexibel ausgeführt, dass bei mechanischem Druck an einem der Elementeenden der Abstand zwischen diesen verändert wird. Die Veränderung wird als Messeffekt ausgenutzt. The invention is based on the magnetostrictive effect. Magnetostrictive sensors as well as various measuring and signal evaluation methods for these have been known for a long time. Roughly generalized, magnetostrictive sensors can be divided into two functional groups and two technological groups. One group exploits the magnetostrictive effect, the other the inverse magnetostrictive effect. In the technological classification, one of the magnetic or the magnetostrictive element is designed to be so flexible with respect to the other that with mechanical pressure at one of the element ends, the distance between them is changed. The change is exploited as a measuring effect.
Verfahrungen und Vorrichtungen, die das Auswerteergebnis abstandsunabhängig von der Distanz Sensorelement/Messobjekt um ein Vielfaches des Messeffektes übersteigen, sind genauso bekannt wie Auswerteschaltungen, die ein nahezu lineares Messergebnis zum Span- nungszustand des magnetostriktiven Materials liefern. Procedures and devices that exceed the evaluation result distance-independent of the distance sensor element / measurement object by a multiple of the measurement effect, are just as well known as evaluation circuits that provide a nearly linear measurement result to the voltage state of the magnetostrictive material.
In der Offenlegungsschrift DE 35 34 460 A1 [Sensoranordnung] wird eine Anordnung beschrieben, die eine erweiterte Linearisierung der Transferkennlinie ermöglicht. Eine Messbe- reichslinearisierung wird ebenfalls in der DE 36 24 846 A1 [Vorrichtung zum berührungsfrei- en Messen einer mechanischen Spannung] beschreiben. In the patent application DE 35 34 460 A1 [sensor arrangement], an arrangement is described which allows an extended linearization of the transfer characteristic. A measuring range linearization is also described in DE 36 24 846 A1 [device for non-contact measurement of a mechanical stress].
Die DE 36 20 412 A1 [Schaltungsanordnung zum Betreiben eines magnetoelastischen Sensors] beschreibt eine abstimmbare Schaltung, bei der der Abstand Sensorelement-Messobjekt nahezu keinen Einfluss mehr auf das Sensorsignal hat. Das US-Patent 3,898,55 [Linear Di- stance Measuring Device Using a Moveable Magnet Interacting with a Sonic Waveguide] benutzt eine Signallaufzeit zur Signalauswertung mit extrem hoher Signalauflösung. Als vorteilhafte Ausgestaltung wird ein Schirmsystem angegeben, wodurch die Robustheit gegenüber Umwelteinflüssen verbessert wird, als auch die EMV-Eigenschaften der Messeinrichtung. Gemeinsam ist allen Anordnungen und Verfahren, das die Signalauswertung entweder direkt analog oder über das Mischungsprodukt oder die Mischsumme als frequenzselektive Auswertung erfolgt. Gemeinsam nachteilig ist allen Auswerteverfahren, dass sie die Amplituden der Harmonischen der Modulationsfrequenz und deren Verlauf in Abhängigkeit des Spannungs- zustandes des magnetostriktiven Materials betrachten und auswerten, auch nicht die Verhältnisse zwischen diesen Harmonischen. DE 36 20 412 A1 [circuit arrangement for operating a magnetoelastic sensor] describes a tunable circuit in which the distance sensor element measuring object has almost no influence on the sensor signal. US Pat. No. 3,898,55 (Linear Device Measuring Device Using a Movable Magnet Interacting with a Sonic Waveguide) uses a signal propagation time for signal evaluation with extremely high signal resolution. As an advantageous embodiment of a shielding system is specified, whereby the robustness against environmental influences is improved, as well as the EMC properties of the measuring device. Common to all arrangements and methods, the signal evaluation is either directly analog or via the mixture product or the mixed sum as a frequency-selective evaluation. A common disadvantage of all evaluation methods is that they do not consider and evaluate the amplitudes of the harmonics of the modulation frequency and their course as a function of the voltage state of the magnetostrictive material, nor the relationships between these harmonics.
Der Erfindung liegt die Aufgabe zugrunde, ein Auswerteverfahren bereitzustellen, das es ermöglicht, ein zeitmoduliertes Signal zu gewinnen, das für die magnetischen Eigenschaften eines invers magnetostriktiven Materials charakteristisch ist. The object of the invention is to provide an evaluation method which makes it possible to obtain a time-modulated signal which is characteristic of the magnetic properties of an inverse magnetostrictive material.
Die Aufgabe wird durch ein Verfahren mit den im Anspruch 1 gelöst. Die Unteransprüche geben ebenfalls vorteilhafte Ausführungen an. Grundgedanke des Verfahrens ist die Betrachtung bestimmter Fourier-Koeffizienten bzw. deren Nullstellen, was ein berührungsloses Auslesen über sehr große Distanzen in Bezug auf den Messeffekt ermöglicht. The object is achieved by a method with the in claim 1. The dependent claims also indicate advantageous embodiments. The basic idea of the method is the consideration of certain Fourier coefficients or their zeros, which enables a non-contact reading over very large distances in relation to the measuring effect.
Ein Ausführungsbeispiel des Verfahrens wird im Folgenden zunächst allgemein anhand von acht Figuren und einer Tabelle näher erläutert. Dabei zeigt: An exemplary embodiment of the method will initially be explained in more detail below generally with reference to eight figures and a table. Showing:
- Fig. 1 eine idealisierte Magnetisierungskurve, FIG. 1 shows an idealized magnetization curve, FIG.
- Fig. 2 ein magnetisches Material im sinusförmigen Wechselmagnetfeld mit FIG. 2 shows a magnetic material in the sinusoidal alternating magnetic field. FIG
Rechteckverlauf der Suszeptibilität,  Rectangular course of susceptibility,
- Fig. 3 die Koeffizienten der Fourier-Reihe mit Vielfachen der doppelten Modulationsfrequenz, - Fig. 4 die lokalen Minima in Abhängigkeit vom mechanischen Material-FIG. 3 shows the coefficients of the Fourier series with multiples of twice the modulation frequency. FIG. 4 shows the local minima as a function of the mechanical material.
Spannungszustand, Stress state
- Fig. 5a die Fourier-Koeffizienten als Abstandsfunktion zwischen Material und Messspule, Fig. 5b die charakteristischen Minima bei Abstandsvergrößerung, FIG. 5a shows the Fourier coefficients as distance function between material and measuring coil, FIG. 5b the characteristic minima at distance increase,
- Fig. 6 die Rechtecksignal-Tastveränderung bei variiertem Hmod., FIG. 6 shows the square-wave signal change with a varied Hmod. FIG.
- Fig. 7 die Nullstellen der Fourier-Koeffizienten für verschiedene Hmo ^- Verhältnisse, FIG. 7 shows the zeros of the Fourier coefficients for different H mo ^ ratios. FIG.
- Fig. 8 das proportionales Material- Anisotropiefeld für Modulationsfeld mit Nullstellen sowie FIG. 8 shows the proportional material anisotropy field for the modulation field with zeros and. FIG
- Tab. 1 die Nullstellenzusammenstellung nach Gleichung (8). - Tab. 1, the set of zeros according to equation (8).
Ein ferromagnetisches, invers magnetostriktives Material wird einem Wechselmagnetfeld der Frequenz fmod. ausgesetzt. Die Größe des Wechselmagnetfeldes ist dabei so gewählt, dass das magnetische Material periodisch in die Sättigung gebracht wird. Daraus ergibt sich für die Magnetisierungskurve, dargestellt als Magnetisierung M des Materials als Funktion der exter- nen Feldstärke Hext , ein charakteristischer Verlauf der Suszeptibilität über die A ferromagnetic inverse magnetostrictive material becomes an alternating magnetic field of frequency f mo d. exposed. The size of the alternating magnetic field is chosen so that the magnetic material is periodically brought to saturation. For the magnetization curve, represented as the magnetization M of the material as a function of the external field strength H ext , this results in a characteristic course of the susceptibility over the
Zeit.  Time.
Vereinfachend soll im Folgenden zunächst von einer idealisierten Magnetisierungskurve ausgegangen werden [Fig. 1], die sich durch unten aufgeführte Eigenschaften beschreiben lässt: For simplicity's sake, an idealized magnetization curve will initially be assumed in the following text [Fig. 1], which can be described by the properties listed below:
- Die Sättigungsmagnetisierung Ms wird bei der Feldstärke Hk erreicht, The saturation magnetization M s is reached at the field strength H k ,
- die Suszeptibilität* ist für kleine Feldstärken unter dem Anisotropiefeld Hk konstant the susceptibility * is constant for small field strengths below the anisotropy field H k
- durch Anlegen einer äußeren mechanischen Zugspannung σ erhöht sich das Anisotropiefeld Hk, die Sättigungsmagnetisierung Ms bleibt jedoch unverändert. Damit verringert sich die Suszeptibilität mit zunehmender mechanischer Spannung bei positiv magnetostriktive Materialien, wenn die Richtung des Magnetfeldes und die Zugrichtung senkrecht zueinander stehen. - By applying an external mechanical tension σ increases the anisotropy field H k , the saturation magnetization M s remains unchanged. Thus, the susceptibility decreases with increasing mechanical stress in positively magnetostrictive materials when the direction of the magnetic field and the pulling direction are perpendicular to each other.
Damit lässt sich die Magnetisierungskurve durch This allows the magnetization curve through
und die Suszeptibilität durch and the susceptibility through
beschreiben.  describe.
Unterliegt nun das Material mit obiger Magnetisierungskurve einem Wechselmagnetfeld Is now subject to the material with the above magnetization curve an alternating magnetic field
wie m Fig- 2 dargestellt - so ergibt sich für die presented wi em Fig- 2 - then for the
Suszeptibilität ein Rechtecksignal mit den oberen und unteren Werten x und 0 respektive. Zu beachten ist weiterhin, dass sich neben der Amplitude des Rechtecksignals auch das Zeitintervall, in dem das Signal den oberen der beiden Werte einnimmt - entspricht dem Tastverhältnis - mit unterschiedlichen Spannungszuständen verändert. Die Suszeptibilität als Funktion der Zeit lässt sich schreiben als:  Susceptibility a square wave signal with the upper and lower values x and 0 respectively. It should also be noted that in addition to the amplitude of the square wave signal, the time interval in which the signal assumes the upper of the two values-corresponding to the duty cycle-varies with different voltage states. The susceptibility as a function of time can be written as:
Durch die Symmetrie der Magnetisierungskurve - es gilt M(-HexlJ=-M(HextJ - hat das Rechtecksignal x(t) die halbe Periodendauer der Modulationsfrequenz ^ . Es gilt somit für die Periodendauer To des Rechtecksignals: Nun lässt sich das Frequenzspektrum des Rechtecksignals mittels Fourier-Transformation entwickeln. Es gelten hierfür die bekannte Synthese- und Analysegleichung. Sie zeigen, dass jedes Signal eine Grundfrequenz und ein Vielfaches von co0 haben, so dass ein periodisches Signal durch das Gleichungspaar a) der Synthesegleichung Due to the symmetry of the magnetization curve - M (-H exl J = -M (H ext J - the square-wave signal x (t) has half the period of the modulation frequency ^. Thus, the period duration To of the square wave signal is valid: Now the frequency spectrum of the square wave signal can be developed by Fourier transformation. For this, the known synthesis and analysis equation apply. They show that each signal has a fundamental frequency and a multiple of co 0 , so that a periodic signal through the equation pair a) of the synthesis equation
und b) der Anal segleichung - auch als Fourier-Integral bekannt - and b) the analog equation - also known as the Fourier integral -
definiert ist, wobei die Absolutwerte von den Koeffizienten der Fourier-Reihe mit der Grundfrequenz co0 entsprechen. Der Koeffizient a0 ist hierbei der konstante Anteil von x(t) und lässt sich bestimmen durch wherein the absolute values of the coefficients of the Fourier series correspond to the fundamental frequency co 0 . The coefficient a 0 is the constant component of x (t) and can be determined by
Für wird über das Intervall von integriert, was aufgrund der Symmetrie For is integrated over the interval of, due to the symmetry
von x(t) um t=0 günstig ist. T\ sei der Zeitpunkt, bei dem das Rechtecksignal zum ersten Mal auf den Wert null fällt. Für den komplexen Fourier-Koeffizient ax von x(t) ergibt sich of x (t) is favorable by t = 0. T \ is the time at which the square wave first falls to zero. For the complex Fourier coefficient a x of x (t) we obtain
und mit gilt weiter and with applies further
Der Zeitpunkt Ti lässt sich durch die Grenzen von Gleichung (3) im Verhältnis von Ht zu The time Ti can be increased by the limits of equation (3) in the ratio of Ht
Hm0d. ausdrücken. Aus und mitH m0d . express. Off and on
. Gleichung ( -7) erg «ibt dann zusammen mit , Equation (-7) then comes together with
und mit der Gleichung (6) Die Koeffizienten der Fourier-Reihe können damit für ein gegebenes Verhältnis von H* zu Hmod bestimmt werden. Die Koeffizienten für k = 1, ..., 4 sind in Fig. 4 als Funktion dieses Verhältnisses abgebildet. Um das Rechtecksignal und seine Kanten mit geringem Fehler abzubilden, wäre eine Betrachtung bis hin zu hohen Harmonischen notwendig. Da die Amplitude mit steigendem k miti/fc abnimmt, werden in diesem Verfahren nur die ersten vier Harmo- nischen der Messfrequenz fo, d. h. die ersten vier geraden Harmonischen der Modulationsfrequenz fmod. für die Analyse herangezogen. Betrachtet man zudem eine reale Suszeptibilität als Funktion eines externen Magnetfeldes, so gleicht diese ohnehin eher einer Glockenkurve ohne die abrupten Sprünge des hier betrachteten Rechtecksignals. Gemäß Gleichung (8) kann das Auftreten der Nullstellen der ak (für k = 1, 4; siehe Fig. 4) tabellarisch zusammengefasst werden. Tab. 1 zeigt hierfür eine der Möglichkeiten. Dabei ist in der ersten Zeile dasjenige Verhältnis von Hk zu Hm0(j. angegeben, bei dem eines oder mehrere der Fourier-Koeffizienten zu null wird. Der Arkussinus dieses Verhältnisses entspricht einem Bruchteil von π, welcher multipliziert mit 2k für bestimmte k ein Vielfaches von π ergibt. Dies wiederum führt zur Nullstelle des Fourier-Koeffizienten and with the equation (6) The coefficients of the Fourier series can thus be determined for a given ratio of H * to H mod . The coefficients for k = 1, ..., 4 are shown in FIG. 4 as a function of this ratio. In order to map the square wave signal and its edges with a low error, it would be necessary to look at it up to high harmonics. Since the amplitude decreases with increasing k miti / fc, in this method only the first four harmonics of the measuring frequency fo, ie the first four even harmonics of the modulation frequency f mod, become . used for the analysis. If, in addition, a real susceptibility as a function of an external magnetic field is considered, then it is more like a bell curve without the abrupt jumps of the rectangular signal considered here. According to equation (8), the occurrence of the zeros of a k (for k = 1, 4, see Fig. 4) can be summarized in tabular form. Tab. 1 shows one of the possibilities for this. In this case, in the first line, the ratio of H k to H m0 ( j) at which one or more of the Fourier coefficients becomes zero is given, and the arcsine of this ratio corresponds to a fraction of π multiplied by 2k for certain ks This in turn leads to the zero of the Fourier coefficient
Tabelle 1 Table 1
Die Amplitude der Koeffizienten nimmt also exponentiell mit dem Abstand zwischen der Messspule und dem magnetischen Material ab. Die Koeffizienten lassen sich demnach durch beschreiben, wobei ak,o den Koeffizient bei einem Abstand von x = 0 angibt. Die The amplitude of the coefficients thus decreases exponentially with the distance between the measuring coil and the magnetic material. The coefficients can therefore be described by, where a k , o indicates the coefficient at a distance of x = 0. The
Figuren 5a und 5b stellen die Abhängigkeit der Koeffizient von x grafisch dar. Die Fourier-Koeffizienten nehmen also exponentiell mit zunehmendem Abstand x zwischen Messspule und Material ab. Die charakteristischen lokalen Minima treten auch bei zunehmendem Abstand an den gleichen H* zu Hmod auf. Das Verhältnis H* zu Hmod ist demnach entscheidend für die Entstehung von lokalen Minima. So lässt sich umgekehrt auch für jeden Spannungszustand - gekennzeichnet durch ein bestimmtes Hic - das entsprechende Modulationsfeld finden, bei dem ein lokales Minimum auftritt. Die Fourier-Koeffizienten lassen sich nach Gleichung (7) auch für ein sich veränderndes Hmod bei konstantem H* berechnen, wie in Fig. 7 dargestellt. Die Werte des Modulationsfel- des, bei denen Nullstellen der jeweiligen ak für ein bestimmtes Hk auftreten, sind für k = 2, 3, 4 in Fig. 8 gezeigt. Bei konstantem Hk bleibt die Magnetisierungskurve also unverändert. Das Rechtecksignal ändert sich somit bei Variation von Hm0(j. Allein in seinem Tastverhältnis. Die Fourier-Koeffizienten zeigen erneut die Nullstellen bei den entsprechenden Verhältnissen von Hk zu Hmod, bzw. Hmod Zu Hk. Figures 5a and 5b graphically depict the dependence of the coefficient of x. The Fourier coefficients thus decrease exponentially with increasing distance x between the measuring coil and the material. The characteristic local minima also occur with increasing distance at the same H * to H mo d. The ratio H * to H mo d is therefore crucial for the formation of local minima. Conversely, for every stress state - characterized by a specific hic - the corresponding modulation field can be found where a local minimum occurs. The Fourier coefficients can also be calculated according to equation (7) for a changing H mo d at constant H *, as shown in FIG. 7. The values of the modulation field at which zeros of the respective a k occur for a certain H k are shown for k = 2, 3, 4 in FIG. At constant H k , the magnetization curve thus remains unchanged. The rectangular signal thus changes with a variation of H m0 ( j) in its duty cycle alone The Fourier coefficients again show the zeros at the corresponding ratios of H k to H mod , or Hmod to H k .
Das Modulationsfeld, bei dem Nullstellen auftreten, ist demnach proportional zum Anisotropiefeld des Materials. The modulation field where zeros occur is therefore proportional to the anisotropy field of the material.
Durch die Variation des Modulationsfeldes lässt sich also ein bestimmter Fourier-Koeffizient, z. B. Ü4, auf den Wert null minimieren. Der Wert des Modulationsfeldes ist in dieser Nullstelle entsprechend proportional zum Anisotropiefeld des Materials, das wiederum durch den Spannungszustand gekennzeichnet ist. Ändert sich der Spannungszustand des Materials und damit Hk, kann das Modulationsfeld entsprechend angepasst werden, damit der Fourier- Koeffizient weiterhin null beträgt. Diese Möglichkeit der Variation des Modulationsfeldes Hmod. Liefert also eine weitere Möglichkeit der Signalauswertung. By the variation of the modulation field can thus be a certain Fourier coefficient, z. B. Ü4, to zero. The value of the modulation field in this zero position is correspondingly proportional to the anisotropy field of the material, which in turn is characterized by the stress state. If the stress state of the material changes and thus H k , the modulation field can be adjusted accordingly so that the Fourier coefficient remains zero. This possibility of variation of the modulation field Hmod. So provides another way of signal evaluation.

Claims

Ansprüche claims
1. Verfahren zur Bestimmung mechanischer Eigenschaften magnetostriktiver Materialien, mit den folgenden Schritten: 1. A method for determining mechanical properties of magnetostrictive materials, comprising the following steps:
Einbringen des Materials in ein externes Wechselmagnetfeld unter periodischem Sättigen des magnetischen Materials, Introducing the material into an external alternating magnetic field with periodic saturation of the magnetic material,
Aufbringen einer senkrecht zu der Magnetfeldrichtung verlaufenden wechselnden mechanischen Zugspannungsbeanspruchung, Applying a perpendicular to the magnetic field direction alternating mechanical tensile stress,
Gewinnen eines charakteristischen Verlaufs der Suszeptibilität bei verschiedenen Zugbeanspruchungen, Obtaining a characteristic course of the susceptibility at different tensile stresses,
Bestimmen der Koeffizienten einer Fourier-Reihe aus den Verläufen der Suszeptibiltät und Ermitteln der Koeffizienten der sich als lokale Minima darstellenden Nullstellen derDetermine the coefficients of a Fourier series from the tracks of the Suszeptibiltät and determining the coefficients of the local minima representing zeros of the
Fourier-Funktion. Fourier function.
2. Verfahren nach Anspruch 1, gekennzeichnet durch Berücksichtigen allein der Nullstellen einer bestimmten harmonischen Oberschwingung. 2. The method according to claim 1, characterized by taking into account only the zeros of a certain harmonic harmonic.
3. Verfahren nach Anspruch 1 oder 2, gekennzeichnet durch Anpassen des modulierten Magnetfelds derart, dass der Fourier-Koeffizient bei den verschiedenen Zugspannungsbelastungen des magnetischen Materials null wird. A method according to claim 1 or 2, characterized by adjusting the modulated magnetic field such that the Fourier coefficient becomes zero at the various tensile stresses of the magnetic material.
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EP2526434B1 (en) 2015-01-07
WO2011088823A2 (en) 2011-07-28
WO2011088823A3 (en) 2011-11-17

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